Number Sense Video Lessons

Welcome to the Number Sense Lesson page. Here you will find basic number sense tricks. Each video follows the Number Sense Workbook. Once you watch the video, do the extra problems on each page of the workbook. There is a key In the back of the booklet for each section. I just added a new page for Errata in the book at http://mathninja.org/number-sense-workbook-errata/

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If you prefer to have an invoice sent to you via email, please email me at agillespey@yahoo.com with the quantity of books you want and your contact information.Feel free to send me an email with any questions you might have.

Rhythm

I have learned and enjoyed a lot from your awesome Number Sense Workbook so far. I just wanted to let you know that I found a small error on Page 24. On the top right hand corner of that page, the example says that 23 x 38 = 924. However, 23 x 38 = 874.

Thanks for this great book! Hopefully you write a new book, since I really love this one and will get a free copy.

Nice catch. I fixed it in the problem but never the snapshot in the corner of the page. Thanks for pointing that out. Someday im going to get around to making a calculator book and Ill send one your way.

Carol Stringfellow

Sum of two squares (page 54). On these problems either the outer digits add to be ten and the inner digits are one apart OR vice versa. Of the two digits that are one apart, you need to choose the number with the higher digit and proceed with adding the squares of the digits and writing it twice. It is not always the first number that you square the digits and add. What if the problem were written in reverse order? Do you follow what I am saying? When I explain this to my students, I never have been able to make it less wordy. Carol Stringfellow

You are absolutely right. In fact one question this year on a Number Sense test they in fact reversed the two numbers. Now the question is did the writer of the test do that on purpose? If so then we need to make sure the students understand what form it needs to be set up in to be solved. Thanks for the comment.

Math Rocks

Xavier Piña

I am currently watching these videos and my score is increasing. During the school year I was scoring in the 30’s but I started watching these videos 3 days ago and I am currently scoring in the 200’s so Thank You very very much!!!

Math Rocks

I would do it a different way. Since 556 is close to 555, I can “trade” that in for 5/9, and round 247 to 243, which is a multiple of 9 ( I can tell because of the divisibility trick Mr. G put up) and then divide 243 by 9, yielding 27. Then I would multiply 27 by 5, resulting in 135. (BTW, I’ve always found it easier to divide first than multiply first!) Then, I would add back the three zeros I lost when changing 555 to 5/9, yielding 135000, which fits smug in the 5% range of (in this case) 137332.

Priyanka

I have learned a lot from your awesome number sense workbook so far, but I found an error in the answer key. The key states that on page 9, the answer to number 13 is 13, but that cannot be true because 75*88 (number 13 on page 9) is 6600. Thanks for this great workbook! Hopefully you will write a new book, since I really like this one.

Tom

Dear Mr. G,
Thank you creating such wonderful resources for the number sense tests. My score has tremendously improved over the past year.
By any chance do you have any trick for 4^3 times 5^5 or 2^5 times 5^3? (Two different questions)
Thank you once more for the helpful tricks!

Math Rocks

2 to the 5th power times 5 to the third is pretty easy. I didnt know it, but now i do. first you find by how much the exponent is greater than the other exponent. The 5 ( in two to the fifth power) is greater than the 3 (in 5 to the third power) by 2, so you do 2 to the second power. That’s 4, and now you are solving a problem that states 2 to the THIRD power times 5 to the third. Since these have the same “exponent base” you can multiply 2 and 5 to get 10, and do 10 to the third power, which is 1000. now you do the 4 and multiply by 1000, which is 4000. you can use this trick for the other problem u mentioned, and basically all of them. But you’ll usually see 2^x times 5^y ( in 2/5 format) because 2 x 5 is ten, and ten is an easy number to work with, especially in multiplication! Sadly our luck is running out because TMSCA is making the tests harder than ever. Oh yeah, and you might be wondering, “WHO IS THIS GUY?! He’s like on every other comment!” WELL…. If that’s what you’re thinking, I’ll reply to you right now. I’m just trying to help people! I mean no offense to you if you’re NOT thinking that. Just saying………

Absolutely, my own daughter is in 5th grade and she is starting on the book. It takes a long time to get good at number sense. The more time the better. The important thing is that they have a firm grasp of multiplication before working with the book.

Shweta

My daughter has joined math club in 5th gr and my son is in 8thgr they love math. I am just surprised why I never got this book before and never knew about this site before. It’s so much fun and exciting and we have great love and respect for all the teachers for their hard work. Thank you so much! As a woman who loves math and science more than anything else it is great pleasure to see there are people like us who respect teachers and knowledge and school, which other people label boring.
Thank you,
–Shweta